The invention generally relates to the processing of whole blood and its components for storage, fractionation, and transfusion.
With the coming of blood component therapy, most whole blood collected today is separated into its clinically proven components for storage and administration. The clinically proven components of whole blood include, e.g., red blood cells, which can be used to treat chronic anemia; plasma, which can be used as a blood volume expander or which can be fractionated to obtain Clotting Factor VIII-rich cryoprecipitate for the treatment of hemophilia; and concentrations of platelets, used to control thrombocytopenic bleeding.
Along with the growing demand for these blood components, there is also a growing expectation for purity of the blood product. For example, it is believed beneficial that plasma used for transfusion or fractionation be as free as possible of cellular blood species, such as leukocytes, red blood cells, platelets. For example, European Council Guidelines dictate that fresh frozen plasma should contain less than 6.0xc3x97109 residual red blood cells per liter, less than 0.1xc3x97109 residual leukocytes per liter, and less than 50xc3x97109 residual platelets per liter. There is therefore a growing demand for blood processing and storage systems that can treat plasma in a way that removes virtually all cellular blood species.
As another example, the use of photodynamic therapy has been suggested as a way to eradicate infectious agents from collected blood and its components. Still, not all biological contaminants are carried free within the blood where they can be readily coupled to photoactive agents. Some biological contaminants are entrained on or within blood cell species that the plasma carries. It is therefore desirable to remove these blood cell species from plasma for this reason.
The invention provides systems and methods for harvesting plasma that is free or virtually free of cellular blood species.
The systems and methods use tubing adapted to be coupled to a source of plasma. A filter is located in the tubing to separate targeted cellular blood species, such as red blood cells and platelets, from plasma that is conveyed from the source. The filter includes first and second hydrophilic polyvinylidene fluoride (PVDF) membranes having pores sized to remove these targeted cellular blood species from plasma by exclusion.
In one embodiment, the filter includes a prefilter layer that also removes aggregates larger than these targeted cellular blood species from plasma.
In one embodiment, the pores of the first PVDF membrane are larger than the pores of the second PVDF membrane. For example, the pores of the first PVDF membrane are about 1.0 xcexcm in size, and the pores of the second PVDF membrane are about 0.65 xcexcm in size.
In one embodiment, the first PVDF membrane has a porosity that is characterized by a water bubble point of between about 8.5 psi and 13 psi. In this embodiment, the second PVDF membrane has a porosity that is characterized by a water bubble point of between about 15.5 psi and 20.6 psi.
In one embodiment, the filter includes a flexible housing enclosing the first and second PVDF membranes.
In one embodiment, the filter includes a mesh layer in a downstream flow direction from the first and second PVDF membranes.
Other features and advantages of the invention will be pointed out in, or will be apparent from, the drawings, specification and claims that follow.